1.) Technical Field of the Invention
The present invention relates to a semiconductor module incorporating a heat-spreader dissipating heat produced by a semiconductor memory device mounted thereon.
2.) Description of Related Arts
A semiconductor module comprises a plurality of components such as the semiconductor memory device, each of which should be kept at or under a predetermined tolerable operation temperature so that each component can operate to function appropriately.
Especially, since the memory device such as Rambus DRAM running at a high transfer rate, produces enormous heat during the operation, the package of the semiconductor module substantially heats up. Without dissipating heat, the semiconductor module may overheat to malfunction. Therefore, it is critical to maintain the temperature of each component of the semiconductor module less than the predetermined tolerable operation temperature.
In general, a heat-spreader (a heat dissipating plate) is applied for dissipating the heat produced by the semiconductor components mounted on the circuit board, for example, the memory devices so as to prevent the semiconductor module from malfunctioning. The heat-spreader is disposed in contact as widely as possible with each of such semiconductor components to maximize the heat dissipating effect.
Meanwhile, the semiconductor module includes a plurality of semiconductor components, each of which has a height from the surface of the circuit board to the top surface thereof. The height of the semiconductor component is referred to as a xe2x80x9cmounting heightxe2x80x9d hereinafter. The mounting heights of the semiconductor components have deviated from one another, for example, due to the mounting conditions of the semiconductor components. Therefore, in case where the heat-spreader used for the heat dissipating plate is disposed upon the semiconductor components mounted on the circuit board, the semiconductor component having the shorter mounting height cannot reach to and contact with the heat-spreader with a gap therebetween.
As described above, the semiconductor component spaced from the heat-spreader may overheat to malfunction without dissipating heat through the heat-spreader.
In order to solve the problem due to the uneveness of the mounting heights, a conventional semiconductor module takes an approach to dissipate heat produced by the semiconductor components by interposing a thermal sheet with a high thermal conductivity between the heat-spreader and the semiconductor components.
Referring to FIGS. 8A and 8B, the conventional semiconductor module dissipating heat through the thermal sheet and the heat-spreader will be described in detail hereinafter. FIG. 8A is a schematic top view of the conventional semiconductor module, and FIG. 8B is a cross sectional view taken along a line VIIIBxe2x80x94VIIIB in FIG. 8A. As shown in the drawings, the conventional semiconductor module 101 comprises, in general, a circuit board 102 made of material such as epoxy resin and circuit patterns printed thereon (not shown).
The conventional semiconductor module 101 further comprises a plurality of semiconductor components 103 (for example, memory devices 103a, 103b, 103c, 103d), which are mounted on the circuit board 102 and connected with the aforementioned circuit patterns, and a heat-spreader 104 made of material such as metal or alloy of aluminum with a comparatively high thermal conductivity. When the heat-spreader 104 is disposed on the semiconductor components 103, as the mounting heights of the semiconductor components 103 are not even, all of the semiconductor components 103 are not always in contact with the heat-spreader 104, and the semiconductor components 103 with shorter mounting heights are spaced away from the heat-spreader 104 with a gap.
To address this problem, the conventional semiconductor module fills this gap between the semiconductor components 103 and the heat-spreader 104 with the thermal sheet 105 made of material such as resin with a high thermal conductivity. This thermal sheet 105 is made of resin with some flexibility, so that when the heat-spreader 104 presses the thermal sheet 105 against the semiconductor components 103, the thermal sheet 105 can closely contact with both the semiconductor components 103 and the heat-spreader 104. Thus, the conventional semiconductor module 101 can dissipate heat produced by the semiconductor components 103 through the thermal sheet 105 and the heat-spreader 104. As shown in FIG. 8B, the heat-spreader 104 includes a pair of opposing end portions which are bent downwardly to provide a portion for securing the heat-spreader 104 onto the circuit board 102 with a securing member 106 such as rivets.
As described above, the conventional semiconductor module 101 is comprised such that heat generated by the semiconductor components 103 is diffused through the thermal sheet 105, which closely contacts with the semiconductor components 103 and the heat-spreader 104.
However, since the thermal sheet 105 is generally made of resin, it has a thermal conductivity substantially less than that of aluminum metal. This causes heat produced by the semiconductor components 103 to prevent from being diffused enough to the heat-spreader 104. Eventually, this leads the semiconductor components 103 overheated to malfunction when the semiconductor components 103 cannot be kept at or under the predetermined tolerable operation temperature.
To address this problem, an another conventional semiconductor module 101 disclosed in JPA 11-15566, incorporates a thermal sheet 105 (a flexible thermally conductive member) which has a great flexibility and a high thermal conductivity so that the thermal sheet 105 can more closely contact with the heat-spreader 104 and semiconductor components 103 to sufficiently diffuse heat. Yet, this approach raises a problem that the such a thermal sheet 105 having a great flexibility and a high thermal conductivity are made of material such as porous graphite material and multi-metal-film layered material which are quite difficult and expensive to manufacture.
The present invention is addressed to those aforementioned problem, the object of the present invention is to provide a semiconductor module which can effectively dissipate heat generated by the semiconductor components disposed on the circuit board, with a simple structure to manufacture inexpensively.
The semiconductor module according to first aspect of the present invention comprises: a circuit board; a plurality of semiconductor components mounted in a matrix (m lines by n rows, m and n are natural numbers) on the circuit board; and a plurality of heat-spreaders arranged in a matrix (m lines by n rows), each of said heat-spreaders closely contacting each of said semiconductor components; wherein the first line and m-th line of said heat-spreaders are bonded onto said circuit board, and wherein said heat-spreaders at least in lines are bonded to adjacent ones. Thus, even where the mounting heights of the semiconductor components are deviated one another, since each of the heat-spreaders is individually assembled onto the circuit board in a simple manner, to closely contact with the semiconductor components. Therefore, the semiconductor module of the present invention can effectively dissipate heat generated by the semiconductor components directly through the heat-spreaders with a simple structure to manufacture inexpensively.
According to the semiconductor module of the present invention, the natural number n is 1, and m pieces of the heat-spreaders are arranged in a line, and wherein m pieces of the heat-spreaders are bonded to adjacent ones.
According to the semiconductor module of the present invention, each of the heat-spreaders has a step portion with a predetermined height, and wherein the heights of the heat-spreaders is greater than those of the semiconductor components and shorter than those of the the heat-spreaders.
The semiconductor module according to second aspect of the present invention comprises: a circuit board; a plurality of semiconductor components mounted in a matrix (m lines by n rows, m and n are natural numbers) on the circuit board; and a plurality of heat-spreaders arranged in a matrix (m lines by n rows) to closely contact each of the semiconductor components; wherein said heat-spreaders are bonded onto said circuit board. Thus, even where the mounting heights of the semiconductor components are deviated one another, since each of the heat-spreaders is individually bonded or secured onto the circuit board in a simple manner, so as to closely contact with the semiconductor components. Therefore, the semiconductor module of the present invention can effectively dissipate heat generated by the semiconductor components directly through the heat-spreaders with a simple structure to manufacture inexpensively.
According to the semiconductor module of the present invention, each of the heat-spreaders has a step portion with a predetermined height that are substantially the same as those of the semiconductor components.
The semiconductor module according to third aspect of the present invention comprises: a circuit board; a plurality of semiconductor components mounted in a matrix (m lines by n rows, m and n are natural numbers) on the circuit board; and a heat-spreader having a plurality of contacting regions arranged in a matrix (m lines by n rows) to closely contact each of the semiconductor components; wherein said heat-spreaders are bonded onto said circuit board. Therefore, the semiconductor module of the present invention can effectively dissipate heat generated by the semiconductor components directly through the heat-spreaders with a simple structure to manufacture inexpensively.
According to the semiconductor module of the present invention, the heat-spreader includes at least one opening around each of the contacting regions. Such an integrated heat-spreader with preferably many openings increases its flexibility so that the heat-spreader can be easily curved to more strongly press each semiconductor component toward the circuit board. Therefore, the semiconductor components can closely contact with the heat-spreader without leaving a gap therebetween even where the mounting heights of the semiconductor component are different from one another. Eventually, the semiconductor module can effectively dissipate heat generated by the semiconductor components.
The semiconductor module of the present invention, comprises bonding means for bonding said first line and m-th line of said heat-spreaders onto said circuit board; wherein the circuit board incorporates a heat-diffusing member with a high thermal conductivity, and wherein at least one bonding means contacts with the heat-diffusing member. Thus, heat generated by the semiconductor components can be diffused through the thermal sheet and the heat-spreader not only to the atmosphere but also to the metal-core material further through the bolts. Thus, the semiconductor module can more effectively dissipate heat generated by the semiconductor components with a simple module structure.
The semiconductor module of the present invention, comprises bonding means for bonding said heat-spreaders onto said circuit board; wherein the circuit board incorporates a heat-diffusing member with a high thermal conductivity, and wherein at least one bonding means contacts with the heat-diffusing member. Thus, heat generated by the semiconductor components can be diffused through the thermal sheet and the heat-spreader not only to the atmosphere but also to the metal-core material further through the bolts. Thus, the semiconductor module can more effectively dissipate heat generated by the semiconductor components with a simple module structure.
According to the semiconductor module of the present invention, each of the heat-spreaders with a region contacting with each of the semiconductor components is formed so that the region is as wide as possible.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the sprit and scope of the invention will become apparent to those skilled in the art from this detailed description.